"Nguyen wanted to make games for people like himself: busy, harried, always on the move. "I pictured how people play," he says, as he taps his iPhone and reaches his other hand in the air. "One hand holding the train strap." He'd make a game for them."

I found myself playing in this exact manner many times while riding the subway. Even when I would go just one or two stops, it was convenient way to spend the time squeezing in a few games of Flappy Bird without worrying about concentrating too hard on any one game, or being concerned about getting cutoff in any one round by having to leave or dodge a bystander.